Subscriber station for a bus system and method for increasing the data rate of a bus system

ABSTRACT

In a method for increasing the data rate of a bus system in which at least at times an exclusive, collision-free access of a subscriber station to a bus line of the bus system is ensured, a subscriber station for the bus system includes a communication control device for evaluating a message that was received by at least one further subscriber station of the bus system via the bus system, the communication control device including at least two RX protocol machines that are set up to use different bit timing parameter data sets in order to evaluate whether the received message is valid, the at least two RX protocol machines each being assigned a register to which the associated RX protocol machine is designed to write the result of its evaluation of the received message.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to DE 102018 202 615.7, filed in the Federal Republic of Germany on Feb. 21,2018, the content of which is hereby incorporated by reference herein inits entirety.

FIELD OF THE INVENTION

The present invention relates to a subscriber station for a bus systemand to a method for increasing the data rate of a bus system, in which areceived bus signal is redundantly evaluated with different bit timingparameters in order to enable realization of a secure communication inthe bus system with as high a transmission rate as possible even whenthere is distortion of a signal level, in particular relating toradiation relevant for electromagnetic compatibility (EMC).

BACKGROUND

For the transmission of information between subscriber stations of a bussystem, the information is converted by the subscriber stations into asignal having different voltage states that can be transmitted betweenthe subscriber stations serially or in parallel via a bus of the bussystem. In particular, here a communication between sensors and controldevices is conceivable, as takes place for example in a vehicle or in anindustrial production facility, etc. As an example of a serial bussystem, the CAN bus system, and its further developments such as TTCAN(Time Trigger CAN), CAN FD, etc., are in wide use.

In particular, CAN FD, which is described in ISO11898-1:2015 as a CANprotocol option, enables an increase of the data transmission rate in adata phase. In this way, the constantly increasing number of intelligentsensors and increasing networking of control devices in the vehicle, andthus the increasing number of subscriber stations at the CAN bus and thedata traffic at the CAN bus, can be handled. In a CAN FD bus system, adata transmission rate of greater than 1 Mbit per second (1 Mbps) ispossible, for example 2 Mbit/s, 5 Mbit/s, or any other data transmissionrate greater than 1 Mbit/s, etc. In addition, a CAN-HS (HS=high speed)bus system is known in which a data transmission rate of up to 500 kbitper second (500 kbps) is known.

In standard bus topologies, which are intended to connect as manysubscriber stations to one another as possible, CAN subscriber stationsare connected to the bus by stub lines. A problem here is thatreflections occur at each branch of the bus line during the datatransmission. These reflections are superposed on the original signalsand interfere with the reception at the receiver. The greater thereflections are, the slower the data rate has to be selected in order tobe able to reliably transmit or receive the signal. Here, the shorterthe line between the interference source and the receiver, and thelonger the line between the transmitter and receiver, the worse thesignal quality.

Another problem is that in the design of a CAN network or bus system,for each individual subscriber station, the times at which a bit is tobe sampled are set. This setting is also called bit timing. Depending onwhich subscriber station receives the signal, different times areoptimal for error-free reception. However, the times cannot be varied asa function of the transmitting subscriber station. Therefore, in thedesign of a CAN network or bus system, a compromise has to be found forthe best times, taking into account all the subscriber stations. Inparticular in the design of a network having a plurality of CAN-FDsubscribers, it is difficult to set the times in such a way that allsubscribers can receive the signal without error. If new subscriberstations are later to be added to the bus system, it can happen that thecompromise previously found for the best times is no longer the bestcompromise for the then resulting bus system. Ultimately, all thiscauses a reduction of the data rate in the bus system.

SUMMARY

An object of the present invention is to provide a subscriber stationfor a bus system and a method that solve the problems noted above. Inparticular, a subscriber station for a bus system and a method are to beprovided with which a data transmission speed can be realized in the bussystem that is as high as possible even when there is interference onthe CAN bus, such as unfavorable EMC conditions or EMC radiation.

This object is achieved by a subscriber station for a bus system, thesubscriber station including a communication control device forevaluating a message that was received by at least one furthersubscriber station of the bus system via the bus system, in which bussystem at least at times an exclusive, collision-free access of asubscriber station to a bus line of the bus system is ensured, thecommunication control device having at least two RX protocol machinesthat are set up to use different bit timing parameter data sets in orderto evaluate whether the received message is valid, each of the at leasttwo RX protocol machines being assigned a register to which theassociated RX protocol machine is designed to write the result of itsevaluation of the received message.

With the subscriber station, the data transmission speed or datatransmission rate can be increased compared to previous bus systems.This holds even if only one subscriber station of the bus system isrealized as described above. However, the maximum increase can bereached if all subscriber stations of the bus system are designed asdescribed above.

In addition, the design of the bus system is simplified because thesettings of the parameters for a bit timing are automatically carriedout during operation of the bus system. As a result, control devices,actuators, and sensors can on the one hand be used as subscriberstations in different buses without having to adjust the software forthe bit timing or the correct baud rate upon commissioning. On the otherhand, the automatic setting is very advantageous in applications inwhich more and more subscriber stations from different manufacturers areconnected to the bus line over time. Moreover, the bit timing reacts tochanges in the environmental conditions, such as temperature and/orhumidity, etc., automatically, so that the optimal transmission rate inthe bus system is possible under all conditions. As a result, it is nolonger required to reduce the data rate of the bus if no suitable timepoint for error-free reception can be found.

Thus, the subscriber station is also suitable for use in higher-clockedsystems, such as CAN-FD, etc. In addition, the described design of thesubscriber station can also be supplemented as an additional functionfor already-existing subscriber stations designed for communication withan arbitrary CAN protocol. The above-described subscriber station issuitable for use by CAN-FD even in applications in which no furtherincrease of the data rate was possible until now. Such applicationsinclude for example bus topologies in which CAN-FD was previously notusable due to line reflections. Here, it can be sufficient to design inthe manner designed above only those subscriber stations that areaffected particularly strongly by line reflections. However, the maximumbenefit is gained if all subscriber stations of the bus system aredesigned in the manner described above.

The subscriber station can in addition have a comparator unit forcomparing data of the registers, and in addition can have a receivememory for receiving valid data of one of the registers, if a test basedon a message identifier included in the received message was successful,and for forwarding the valid data to an interface to a control device ofthe subscriber station.

According to an example embodiment, the communication control device isdesigned to hold available additional parameter data sets and associatederror counters in addition to the bit timing parameter data sets thatare assigned to the at least two RX protocol machines, the at least twoRX protocol machines being designed to exchange their bit timingparameter data set for one of the additional parameter data sets as afunction of the result of the evaluation of the received message, and toselect the additional parameter data set on the basis of the value ofthe associated error counter.

In an example embodiment, the communication control device is designedto hold available a first bit timing parameter data set for a firstphase in which all subscriber stations can transmit simultaneously to abus line of the bus system, an to hold available a second bit timingparameter data set for a second phase in which an exclusive,collision-free access of a subscriber station to the bus line of the bussystem is ensured.

According to an example embodiment, the communication control device isdesigned to replace errored pieces of data stored in a first registerwith valid pieces of data stored in a second register, the communicationcontrol device being designed to take over the bit timing parameter dataset for the RX protocol machine assigned to the first register, whichdata set is used by the RX protocol machine that is assigned to thesecond register and that has received the valid pieces of data.

In an example embodiment, the communication control device is designedto wait until a valid message has been received before the first sendingof a message.

According to an example embodiment, at least two communication controldevices are provided that are connected to bus lines for two differentbus systems, each communication control device having an RX protocolmachine with an associated register to which the associated RX protocolmachine writes the result of its evaluation of the received message, andthe subscriber station having at least two additional RX protocolmachines each having a register to which the associated RX protocolmachine writes the result of its evaluation of the received message, theat least two additional RX protocol machines being optionally assignableto the RX protocol machines.

In an example embodiment, the communication control device is designedto check whether the received message is intended for the subscriberstation or not, and, in the case of an error, to send an error messagefor the received message only if the test yields the result that thereceived message is intended for the subscriber station.

The subscriber station described above can be part of a bus system thathas a bus line and at least two subscriber stations connected to oneanother via the bus line in such a way that they can communicate witheach other. Here, at least one of the at least two subscriber stationsis a subscriber station as described above.

According to an example embodiment, a method for increasing the datarate of a bus system includes evaluating, using a communication controldevice, a message that was received by at least one further subscriberstation of the bus system, in which bus system at least at times anexclusive, collision-free access of a subscriber station to a bus lineof the bus system is ensured, the communication control device having atleast two RX protocol machines that use different bit timing parameterdata sets in order to evaluate whether the received message is valid,and each of the at least two RX protocol machines being assigned aregister to which the associated RX protocol machine writes the resultof its evaluation of the received message. The method offers the sameadvantages as those mentioned above in relation to the subscriberstation.

Further possible implementations of the present invention also includecombinations not explicitly named of features or example embodimentsdescribed above or in the following in relation to the exampleembodiments. Here, the person skilled in the art will also understandindividual aspects to the respective basic form of the present inventionas improvements or supplementation.

In the following, the present invention is described in more detail onthe basis of example embodiments with reference to the accompanyingdrawing in which identical or functionally identical elements have beenprovided with the same reference characters, unless otherwise indicated.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a simplified schematic diagram of a bus system according toan example embodiment of the present invention.

FIG. 2 shows a schema explaining a bit timing in relation to a bit timein the bus system according to an example embodiment of the presentinvention.

FIG. 3 shows a simplified schematic diagram explaining the design of asubscriber station according to an example embodiment of the presentinvention.

FIG. 4 shows a simplified schematic diagram explaining the design of abus system protocol machine according to an example embodiment of thepresent invention.

FIG. 5 shows a simplified schematic diagram explaining the design of abus system protocol machine according to an example embodiment of thepresent invention.

FIG. 6 shows a simplified schematic diagram explaining the design of asystem of bus system protocol machines according to an exampleembodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a bus system 1 that can be for example a serial bus system,in particular a CAN bus system, a CAN-FD bus system, etc. Bus system 1can be used in a vehicle, in particular a motor vehicle, an aircraft,etc., or in a production facility, in a hospital, etc. Even though, inthe following, the present invention is explained on the basis of theCAN bus system, this is not limiting. Instead, the principle of thepresent invention can be used with some other serial bus system.

In FIG. 1, bus system 1 has at least two subscriber stations 10, 20, 30,each connected to a bus line 40 having two bus leads 41, 42. Subscriberstations 10, 20, 30 are for example control devices, display devices, orsensors or actuators of a motor vehicle. Via bus line 40, messages 45,46, 47 can be transmitted between the individual subscriber stations 10,20, 30 in the form of signals. Messages 45, 46, 47 each has one of themessage identifiers 451, 461, 471, which in CAN bus systems can also becalled CAN-ID. The message identifier 451, 461, 471 unambiguouslyidentifies the subscriber station that sent the associated message 45,46, 47.

As shown in FIG. 1, subscriber station 10 has a communication controldevice 11 and a transceiver device 12. Subscriber station 20 has, incontrast, a communication control device 21 and a transceiver device 12.Like subscriber station 10, subscriber station 30 has a communicationcontrol device 11 and a transceiver device 12. Transceiver devices 12 ofsubscriber stations 10, 20, 30 are each connected directly to bus line40, although this is shown only in FIG. 2.

Communication control device 11 of FIG. 1 is used to control acommunication of the respective subscriber station 10, 20, 30 via busline 40 with another subscriber station of the subscriber stations 10,20, 30 connected to bus line 40. With regard to its transmitfunctionality, communication control device 11 can be realized as aconventional CAN controller. Transceiver device 12 can be realized as aconventional CAN transceiver. Subscriber station 20 corresponds, withregard to both its transmit and its receive functionality, to aconventional CAN subscriber station.

In a CAN bus system, a plurality of subscriber stations 10, 20, 30 canat times simultaneously send out messages 45, 46, 47 having messageidentifiers 451, 461, 471. These message identifiers 451, 461, 471 areused for arbitration in the arbitration phase. After the arbitration,there follows a data phase in which only one of the subscriber stations10, 20, 30 sends signals to bus line 40 in the form of one or more ofthe messages 45, 46, 47. This one of the subscriber stations 10, 20, 30has to send message 45, 46, 47 with the highest priority, and hastherefore won the arbitration. From this moment, each listeningsubscriber station 10, 20, 30 can watch for and receive bus signals ormessages 45, 46, 47. In this phase of the communication, also called thedata phase, the data that are actually to be transmitted betweensubscriber stations 10, 20, 30 are sent.

According to FIG. 2, for this purpose subscriber station 10 is designedin such a way that transceiver device 12 receives signals from bus leads41, 42. In a CAN bus system, these signals are designated CAN_H andCAN_L, and form, on bus leads 41, 42, a differential voltageVDIFF=CAN_H−CAN_L as bus signal, as is known. From the analog signalsCAN_H and CAN_L, transceiver device 12 forms a digital receive signalRxD and sends it to communication control device 11. If subscriberstation 10 is active as sender, communication control device 11 sends adigital transmit signal TxD to transceiver device 12. Depending on thereceived receive signal RxD, transmit signal TxD is an error message458, as described in more detail below. From digital transmit signalTxD, transceiver device 12 forms analog signals CAN_H and CAN_L, andsends these to bus leads 41, 42, as is known.

As FIG. 2 shows, communication control device 11 of subscriber station10 has for this purpose, inter alia, a bus system protocol machine 111,an acceptance filter 112, a receive buffer 113 for storing received data450 assessed as valid, a primary transmit memory 114 for storing data455 to be transmitted with high priority, a secondary transmit memory115 for storing data 456 to be transmitted with low priority, and aninterface 116 to a control device 15 of subscriber station 10 that forexample is a sensor or an actuator or an electronic control unit andthat produces data 455, 456 to be transmitted or further processes thevalid received data 450. Via interface 116, communication control device11 and control device 15 exchange signals S_AHP or S_AHB_L andcommunication control device 11 can send an interrupt signal S_IR tocontrol device 15. Moreover, communication control device 11 has aprescaler 117 that, using a whole-number divisor, divides a clock signalS_CLK from control device 15 down to a signal having a lower frequencyfor communication control device 11.

Differing from a conventional communication control device,communication control device 11 of FIG. 2 has at least two RX protocolmachines, namely, in the present example, a first RX protocol machine1111, a second RX protocol machine 1112, and a third RX protocol machine1113, each of which receives receive signal RxD as data 451, 452, 453.Moreover, a comparator unit 118 is provided that is connected downstreamfrom RX protocol machines 1111-1113. In addition, communication controldevice 11 has, as is standard, a TX protocol machine 1115 that producestransmit signal TxD and sends it to transceiver device 12.

First RX protocol machine 1111 evaluates receive signal RxD on the basisof bit timing parameters of a first bit timing parameter data set C1 ofa bit time t_B, from which data 451 result. Bit time t_B is the temporallength of an individual bit of digital receive signal RxD and isdescribed more precisely below in connection with FIG. 3 and associatedbit timing parameters. The result of the evaluation is written to afirst register R1 by first RX protocol machine 1111.

Second RX protocol machine 1112 evaluates receive signal RxD on thebasis of bit timing parameters of a second bit timing parameter data setC2 of bit time t_B, resulting in data 452. The result of the evaluationis written by second RX protocol machine 1112 to a second register R2.

Third RX protocol machine 1113 evaluates receive signal RxD on the basisof bit timing parameters of a third bit timing parameter data set C3 ofbit time t_B, resulting in data 453. Third RX protocol machine 1113writes the result of the evaluation to a third register R3.

The at least two RX protocol machines 1111-1113 operate simultaneouslyduring the reception of digital receive signal RxD, but with differentsettings, namely bit timing parameter data sets C1-C3 in the presentexample, and write the received data 451 first to separate registersR1-R3. Comparator unit 118 compares data 451-453 with each other. Thisis described in more detail below.

FIG. 3 illustrates the bit timing parameters of bit time t_B for anindividual bit 410 in more detail. At the beginning of bit 410, or atthe beginning of bit time t_B, there is situated a sync segment 4101 atthe beginning of which an edge recognition takes place, at time t_F1,and at the end of which an edge recognition takes place at time t_F2.

In addition, following sync segment 4101, individual bit 410 has asignal propagation segment 4102, followed by two successive phasesegments 4103, 4104. Between first phase segment 4103 and second phasesegment 4104 there is situated a sampling time t_A at which the voltagestate or voltage level of bit 410 is sampled. Depending on the length ofthe two phase segments 4103, 4104—different lengths or time durations ofphase segments 4103, 4104 also being possible—sampling time t_A can beshifted within bit time t_B. The length or time duration of signalpropagation segment 4102 is a function in each case of the topology ofbus line 40, the number of subscriber stations 10, 20, 30, the spatialdistance between the individual subscriber stations 10, 20, 30, thenumber and length of the stub lines for connecting subscriber stations10, 20, 30 to bus line 40, etc.

If the edges of bit 410 are distorted by EMC radiation, it can occurthat bit 410 is lost during reception or cannot be acquired. Moreover,an error can occur if bit 410 is sampled at an unfavorable sampling timet_A. Generally, EMC radiation can distort the level of bit 410 sostrongly that, even given sampling at an optimal sampling time t_A, anerrored bit 410 is received, while bit 410 can be received without errorif sampling takes place shortly before or shortly after the optimalsampling time t_A.

Therefore, sampling time t_A is the main element to be varied. For thispurpose, a freely selectable combination of the following selectableparameters is defined for each of the various bit timing parameter datasets C1-C3, it being possible that the various bit timing parameter datasets C1-C3 differ only in at least one of the parameters named below.Primarily, these are the bit timing parameters, which are described inISO11898-1:2015:

a. Prescaler m

b. Prop_Seg

c. Phase_Seg1

d. Phase_Seg2

e. SJW

A variation of these parameters implicitly also enables the bit rates tobe varied.

Thus, if one of the RX protocol machines 1111-1113 of FIG. 2 receivesimplausible data from receive signal RxD, which is based on a message45, for example data 451 of machine 1111, then, using comparator unit118 and acceptance filter 112, it is checked whether one of the other RXprotocol machines 1112, 1113 can receive plausible data from receivesignal RxD.

By evaluating a checksum (CRC sum) at the end of data 451-453,comparator unit 118 decides whether the reception was correct. Thereception was correct if the evaluation of the checksum (CRC sum) at theend of data 451-453 provides a valid result (CRC=OK). Otherwise, thereception was not correct. At the end of message 45, communicationcontrol device 11 always reports back to bus 40, with an acknowledgebit, as to whether the reception was correct or not.

As long as one of the RX protocol machines 1111-1113 can receive validor plausible data from receive signal RxD, comparator unit 118 decidesthat the reception will be continued even if individual RX protocolmachines 1111-1113 receive errored data. If all other RX protocolmachines 1111-1113 receive no plausible data from receive signal RxD,then the reception is aborted by an error message 458.

If, after the reception, at least two registers of registers R1-R3contain data 451, 452, 453 that are valid or plausible, but differentfrom one another, then the content of message 45 is discarded and anerror message 458 is sent as transmit signal TxD. This can take place asfollows. If at least two of the RX protocol machines 1111-1113 receivedifferent but valid data 451-453 at different times, the acknowledge bitcan be sent as soon as the first RX protocol machine, for example RXprotocol machine 1112, arrives at a valid result after the evaluation ofthe checksum. If, as the process continues, additional RX protocolmachines also receive valid but different data 451, 452, 453 of messages45, then communication control device 11 sends an error message 458instead of another acknowledge bit.

As an alternative to the above procedure of communication control device11, in which an error message 458 is sent instead of a furtheracknowledge bit, the procedure can even more advantageously be asfollows. If communication control device 11 has sent an acknowledge bitonce, then no further action is permitted to be taken based on thereceive result of the other RX protocol machines. That is, communicationcontrol device 11 is permitted neither to send an error message 458based on the receive result of the other RX protocol machines, nor tosend a further acknowledge bit. In this case, the other RX protocolmachines can simply abort their operation in connection with thereception of the current message 45, and wait for the next message.

If one of the registers R1-R3 contains valid data 451, 452, 453, or ifat least two of the registers R1-R3 contain valid data 451, 452, 453that agree with each other, then these are written to receive buffer 113as data 450, if a check of the ID, or of message identifier 451, ofmessage 45 by acceptance filter 112 was successful. The check byacceptance filter 112 is successful if data 450 are relevant for controldevice 15.

The acceptance filtering carried out by acceptance filter 112 thusdecides whether or not a message 45, or its data 451, are stored inreceive memory 113 as data 450.

Thus, for various configurations of bus system 1, subscriber stations10, 30 can receive valid data 450 from the RxD receive signal. In thisway, the data rate of bus system 1 can be increased compared to aconventional bus system. In this way, subscriber stations 10, 30 carryout a method for increasing the data rate of bus system 1.

According to a modification of the example embodiment described above,the case is taken into account in which subscriber station 10, inparticular a sensor, etc., is to be used in many different bus systems 1that have different overall lengths, clock frequencies, and numbers ofsubscriber stations. In this case, it is advantageous to proceed asfollows. After the initial operation of subscriber station 10 in bussystem 1, subscriber station 10 waits to first send a message 45 untilsubscriber station 10 is able to receive a valid message 45 or validdata 450. As soon as this has successfully taken place, subscriberstation 10 can ascertain, from the associated data set C1-C3, the baudrates with which operation is taking place in bus system 1. Onlystarting from this time does subscriber station 10 send its data, withthe baud rates used in the bus. In this way, subscriber station 10 canbe used in bus systems 1 having any configuration, without softwaremodification.

According to a further modification of the example embodiment describedabove, communication control device 11 can be informed, by an additionalitem of information in receive registers R1-R3, as to how many RXprotocol machines 1111-1113 have received message 45 without error.Communication control device 11, in particular its software, can thendecide whether the number of error-free evaluations is sufficient and/orwhether the received information or data 450 is/are trustworthy enough,and/or whether the signal quality is adequate to allow this to be usedin safety-relevant decisions, or to abort the signal transmissionthrough an error message 458, and/or to repeat it. If desired, thesignal transmission can be better secured with the lower protocol layersthan has been possible up to now. Such a procedure is advantageous ifparticular value is placed on avoiding failure to notice erroredreception of messages 45, 46, 47. This is the case for example if data450 are not to be secured by higher protocol layers.

FIG. 4 shows a bus system protocol machine 1110 according to an exampleembodiment. Bus system protocol machine 1110 according to this examplecan be used in at least one of the subscriber stations 10, 30 instead ofbus system protocol machine 111 described above. In addition oralternatively, bus system protocol machine 1110 according to the presentexample embodiment can be used in subscriber stations 20. Except for thedifferences described below, bus system 1 is realized in the same way asdescribed above in relation to the first example embodiment and/ormodifications thereof.

In bus system protocol machine 1110 according to the present exampleembodiment, the optimal bit timing parameters for parameter data setC1-C3 can be learned adaptively, as follows. For this purpose, more bittiming configurations Ca, Cb, Cc, Cd, Ce, Cf are stored in a table 60than the number of available RX protocol machines 1111-1113. Table 60can be provided in a data file or in a database. Moreover, for each bittiming configuration Ca, Cb, Cc, Cd, Ce, Cf there is an error counterFa, Fb, Fc, Fd, Fe.

Whenever one of the RX protocol machines 1111-1113 has received amessage 45 with an error, but one of the other RX protocol machines1111-1113 was able to receive message 45 without error, then, after theunsuccessful reception, RX protocol machine 1111-1113 selects as bittiming parameter data set C1-C3 a bit timing configuration Ca, Cb, Cc,Cd, Ce, Cf that was not already selected by any of the other RX protocolmachines 1111-1113 and whose error counter Fa, Fb, Fc, Fd, Fe has thelowest value.

If for example RX protocol machine 1111 having configuration Cf receivesa message 45 with an error, whereas RX protocol machine 1112 havingconfiguration Cb receives message 45 without error, then RX protocolmachine 1111 selects the new configuration Cd, because error counter Fdhas the lowest value of all the configurations remaining for selection.In addition, the value of error counter Ff is increased by 10 points,and the value of error counter Fb is lowered by one point.

If all, or none, of RX protocol machines 1111-1113 receive message 45without error, then the error counter values of error counters Fa, Fb,Fc, Fd, Fe remain the same.

If none of the RX protocol machines 1111-1113 are able to receivemessage 45 without error, then the RX protocol machine 1111-1113 that isusing the configuration having the highest error counter valuesuccessively tries all other configurations Ca, Cb, Cc, Cd, Ce, Cfhaving equal or higher error counter values in error counters Fa, Fb,Fc, Fd, Fe, while all other RX protocol machines 1111-1113 keep theconfigurations Ca, Cb, Cc, Cd, Ce, Cf having the lowest error countervalues.

In this way, the bus system protocol machine 1110 according to thepresent example embodiment can also be adapted to changed bus operatingconditions. In this way, changes in the environmental conditions, suchas temperature and/or air humidity, etc., can be compensated. This isbecause bus system protocol machine 1110 automatically reacts with achanged bit timing on the basis of parameter data set C1-C3 in such away that bit timing configuration Ca, Cb, Cc, Cd, Ce, Cf is selected insuch a way that the optimal transmission rate is possible under allconditions.

In addition, control devices 15, such as control units or actuators orsensors, etc., in different buses can be used without having to adaptthe software for the bit timing or the correct baud rate, because theoptimal bit timing and the correct baud rate are set automaticallyduring running operation through the selection of the optimal parameterdata set C1-C3, Ca, Cb, Cc, Cd, Ce, Cf. In this way, bus system protocolmachines 1110 become substantially lower in cost, and thuscost-effective even in the lowest piece counts.

According to a modification of the example embodiment described above,in addition to the embodiment described above different bit timingparameter sets C1-C3, Ca, Cb, Cc, Cd, Ce, Cf having their own errorcounters F1, F2, F3, Fa, Fb, Fc, Fd, Fe can be held available for thearbitration and data phase of a message 45. The different bit timingparameter sets C1-C3, Ca, Cb, Cc, Cd, Ce, Cf having their own errorcounters F1, F2, F3, Fa, Fb, Fc, Fd, Fe can each be assigned to therespectively present RX protocol machines 1111-1113 independently of oneanother, according to the method described above.

FIG. 5 shows a bus system protocol machine 1118 according to an exampleembodiment. Bus system protocol machine 1118 according to this exampleembodiment can be used in at least one of the subscriber stations 10, 30instead of one of the bus system protocol machines 111, 1110 accordingto one of the preceding example embodiments. In addition oralternatively, bus system protocol machine 1118 according to the presentexample embodiment can be used in subscriber station 20. Except for thedifferences described below, bus system 1 is realized in the same way asdescribed above in relation to the first example embodiment and/ormodifications thereof.

In bus system protocol machine 1118 according to the present exampleembodiment, if, during reception, implausible or errored data 451, oronly pieces thereof, are stored in one of the registers R1-R3, but data452, or only pieces of data, that are recognized as plausible or as nothaving errors are stored in at least one of the other registers R1-R3,the errored data 452, or only pieces of data, are replaced by theplausible data 452 or pieces of data. Moreover, the current bit timingparameter set C1-C3, with which the valid data 452 or pieces of data canbe received, is taken over by the evaluation. The exchange of thecurrent bit timing parameter set C1-C3 is to be understood as meaningthat what is exchanged is the time step in which the last edge of a bit410 was recognized, in order to enable correct determination of samplingtime t_A.

The procedure offers an advantage if, during the transmission of amessage 45, first only reception with, for example, bit timing parameterset C2 is successful, subsequently only reception with the other bittiming parameter set C3 is successful. If data 451, or pieces of data,have to be corrected by one of the RX protocol machines 1111-1113, whiledata 452 or pieces of data do not have to be corrected by other RXprotocol machines 1111-1113, then only the error counters F1, F2, F3,Fa, Fb, Fc, Fd, Fe are increased of the RX protocol machines 1111-1113in which the corrections were necessary. In contrast, the error countersF1, F2, F3, Fa, Fb, Fc, Fd, Fe of the other RX protocol machines1111-1113 are reduced, as described above in relation to FIG. 4.

In this way, disturbances in bus system 1 can be even better compensatedor corrected. In this way, a still greater increase of the datatransmission speed in bus system 1 is possible.

FIG. 6 shows a system of two bus system protocol machines 111A, 111Baccording to an example embodiment. The system stands for the case inwhich a subscriber station 100 has a plurality of bus system protocolmachines 111A, 111B, so that its control device 15 can be connected tobus lines 40, 50 of a plurality of buses. Bus line 50 also has a firstand second bus lead 51, 52. In part, better receive properties arenecessary for the different buses or bus lines 40, 50. In part, however,receive properties that are not as good are adequate. The higher thedemands that are placed on the receive quality, the more RX protocolmachines 1111-1114 having parameter data sets or bit timing parameterdata sets C1-C4 and registers R1-R4 for receiving data 451-454 are to beconnected to this bus or bus line 40. For this reason, it is alsoadvantageous if a respective RX protocol machine 1111A for receivingdata 451A and a TX protocol machine 1115A are always fixedly assigned toa respective bus, but the additional RX protocol machines 1111-1114,together with the associated configuration settings or data sets C1-C4and receive registers R1-R4 for receiving data 451B, can however beassigned variably to the individual buses or bus lines 40, 50.

In the example of FIG. 6, in part better receive properties arenecessary for the bus or bus line 50 because RX protocol machines 1112,1113, 1114 are in addition assigned thereto, whereas only RX protocolmachine 1111 is additionally assigned to the bus or bus line 40.However, a different assignment of RX protocol machines 1111-1114 ispossible.

The number of additional RX protocol machines 1111-1114 to be selectedcan be specified in the design of the system. However, it isalternatively conceivable that the assignment at least of a certainnumber of RX protocol machines 1111-1114 takes place variably duringoperation. It is advantageous to assign more RX protocol machines1111-1114 to a bus the more errored messages 45, 46, 47 are received inbus system 1.

Thus, with all the example embodiments and/or modifications thereofdescribed above, the data transmission rate in bus system 1 can beincreased. As long as only one of the subscriber stations 10, 20, 30operates with the described method according to at least one of theexample embodiments and/or modifications thereof described above, only aslight increase in the data rate is possible. However, as soon as allsubscriber stations 10, 20, 30 use the described method according to atleast one of the example embodiments and/or modifications thereofdescribed above, the full potential can be exploited.

Moreover, the full potential for increasing the data transmission ratein bus system 1 can be exploited if only one of the subscriber stations10, 20, 30 operates with the described method according to at least oneof the example embodiments and/or modifications thereof described above,but the remaining subscriber stations 10, 20, 30 do not send any errormessages 458 via bus line 40 in the case of messages 45, 46, 47 notintended for these subscriber stations 10, 20, 30. For this purpose, theremaining subscriber stations 10, 20, 30 can for example store a list inwhich the message identifiers 451, 461, 471 are stored of subscriberstations 10, 20, 30 of which the other subscriber stations 10, 20, 30 donot process any data.

Alternatively, the remaining subscriber stations 10, 20, 30 can alsocompletely switch off the error handling.

In this way, signals that can be correctly received by particularreceivers are prevented from being destroyed by subscriber stations thatare not participating in the data transmission. In this way, a broaderuse of CAN-FD and a higher maximum data rate on a CAN bus are achievedthan were previously the case.

All embodiments described above of bus system 1 of subscriber stations10, 20, 30 and of the method according to the example embodiments andthe modifications thereof can be used individually or in all possiblecombinations. In addition, in particular the following modifications areconceivable.

Bus system 1 described above according to the example embodiments andmodifications thereof is described on the basis of a bus system based onthe CAN protocol. Bus system 1 according to the example embodiments andmodifications thereof can however also be a different type ofcommunication network. It is advantageous, though not a necessaryprecondition, that in bus system 1, at least for particular time spans,an exclusive, collision-free access of a subscriber station 10, 20, 30to bus line 40, or to a common channel of bus line 40, is ensured.

Bus system 1 according to the described example embodiments is inparticular a CAN network or a CAN FD network or a LIN network or aFlexRay network.

The number and configuration of subscriber stations 10, 20, 30, 100 inbus systems 1 according to the example embodiments and modificationsthereof is arbitrary. In particular, it is also possible for onlysubscriber stations 10 or subscriber stations 30 or subscriber stations100 to be present in bus systems 1 of the example embodiments and themodifications thereof.

In order to achieve a still higher data rate, within the CAN frameworkof messages 45, 46, 47, the data transmission, for example in the dataphase, can take place analogously to other serial data transmissionprotocols such as Ethernet, etc. The functionality of the exampleembodiments described above can be realized in a chipset of acommunication control device 11. In addition or alternatively, it can beintegrated into existing products. In particular, it is possible for thefunctionality under consideration to be embedded either in communicationcontrol device 11 as a separate electronic component (chip) or in anintegrated overall solution in which only one electronic component(chip) is present.

What is claimed is:
 1. A subscriber station for a bus system in which atleast at times an exclusive, collision-free subscriber station access toa bus line of the bus system is ensured, the sub scriber stationcomprising: a communication control device that includes at least two RXprotocol machines that are configured to: for a same message that wasreceived by the subscriber station via the bus system and from at leastone additional subscriber station of the bus system, use differentrespective bit timing parameter data sets to extract data of themessage; and write a respective result of the extraction by therespective RX protocol machine to a respective register assignedrespectively to the respective RX protocol machine.
 2. The subscriberstation of claim 1, further comprising another control device, whereinthe communication control device further includes: a comparatorconfigured to compare data of the registers; and a receive memoryconfigured to store valid data of one of the registers if a check basedon a message identifier included in the received message was successful,and to forward the valid data to an interface to the other controldevice.
 3. The subscriber station of claim 1, wherein: the communicationcontrol device is configured to hold additional parameter data sets andassociated error counters; and each of the at least two RX protocolmachines is configured to exchange its respective bit timing parameterdata set for one of the additional parameter data sets based on therespective evaluation results, and thereby select the respectiveassociated error counter.
 4. The subscriber station of claim 1, whereinthe communication control device is configured to hold: a first bittiming parameter data set for a first phase in which all subscriberstations can transmit simultaneously to the bus line of the bus system;and a second bit timing parameter data set for a second phase in whichan exclusive, collision-free subscriber station access to the bus lineof the bus system is ensured.
 5. The subscriber station of claim 1,wherein the communication control device is configured to: replaceerrored pieces of data that are stored in a first of the registers withvalid pieces of data that are stored in a second of the registers; andreplace the bit timing parameter data set for the RX protocol machineassigned to the first register, with the data set that is used by the RXprotocol machine that is assigned to the second register and that hasreceived the valid pieces of data.
 6. The subscriber station of claim 1,wherein, even after the communication control device having received oneor more messages, the communication control device is configured to waituntil a valid message has been received before a first sending of amessage.
 7. The subscriber station of claim 1, further comprising asecond communication control device, wherein the bus line includes afirst bus line and a second bus line, each of the communication controldevices being connected to a respective one of the bus lines and fixedlyincluding a respective RX protocol machine and respective associatedregister to which the associated RX protocol machine writes the resultof its data extraction, the subscriber station including at least twoadditional non-fixedly assigned RX protocol machines each having aregister to which the respective RX protocol machine writes the resultof its data extraction, the at least two additional RX protocol machinesbeing variably assignable to the first and second bus lines.
 8. Thesubscriber station of claim 1, wherein the communication control deviceis configured to check whether the received message is intended for thesubscriber station, and, in a case of an error, send an error messagefor the received message only if the received message is intended forthe subscriber station.
 9. A bus system comprising: a bus line to whichan exclusive, collision-free subscriber station access is ensured atleast at times; and at least two subscriber stations that are connectedto one another via the bus line in such a way that they can communicatewith one another, wherein at least one of the at least two subscriberstations includes a communication control device that includes at leasttwo RX protocol machines configured to: for a same message that wasreceived by the subscriber station via the bus system and from at leastone additional subscriber station of the bus system, use differentrespective bit timing parameter data sets to extract data of themessage; and write a respective result of the extraction by therespective RX protocol machine to a respective register assignedrespectively to the respective RX protocol machine.
 10. A method forincreasing a data rate of a bus system in which at least at times anexclusive, collision-free subscriber station access to a bus line of thebus system is ensured, the method comprising: evaluating, with acommunication control device of a first subscriber station, a messagethat was received, via the bus system, by at least one second subscriberstation of the bus system, wherein the communication control deviceincludes at least two RX protocol machines that are configured to: for asame message that was received by the subscriber station via the bussystem and from at least one additional subscriber station of the bussystem, use different respective bit timing parameter data sets toextract data of the message; and write a respective result of theextraction by the respective RX protocol machine to a respectiveregister assigned respectively to the respective RX protocol machine.